It is well known in the art that at moderate temperatures and varying pressures chloromethylation of aromatic nuclei can be accomplished with formaldehyde and haloacids or with other chloromethylating agents in the presence of a suitable catalyst. These reactions are well known in the literature.
In U.S. Pat. No. 3,652,689 there is described a liquid phase chloromethylation process as shown below: ##SPC1##
Described in U.S. Pat. No. 3,625,870 is a chloromethylation process using chloromethyl ether and zirconium tetrachloride which is also done in the liquid phase as shown below: ##SPC2##
A process for the polychloromethylation of alkaryl hydrocarbons is disclosed in U.S. Pat. No. 3,422,160 as shown below: ##SPC3##
Wherein the chloromethylating agent is produced by the reaction of formaldehyde and a halogen acid generating agent such as PCl.sub.3.
Chloromethyl benzene has also been produced by the reaction of formaldehyde and halogen acid using sulfur compounds containing halogen as a catalyst, as shown in U.S. Pat. No. 3,271,465 below: ##SPC4##
U.S. Pat. No. 2,973,891 describes a liquid phase chloromethylation of benzene using zinc chloride in the presence of an alkali metal or alkaline earth chloride as shown below: ##SPC5##
A selective monochloromethylation and dichloromethylation at varying pressures has been accomplished using formaldehyde and aqueous hydrochloric acid in the presence of zinc chloride as described in U.S. Pat. No. 2,951,100. It has been reported that various mixtures of .alpha.- and .beta.- chlorostyrenes and dichlorostyrenes can be prepared by the chlorination of styrenes via ultraviolent light and low temperatures as described in the work published by Sadykh-Zade et al. The art also describes in U.S. Pat. No. 2,981,758 the chlorination of alkyl vinyl aromatic compounds at relatively high temperatures without chlorinating the vinyl group as shown below: ##SPC6##
Finally the art teaches in U.S. Pat. No. 2,780,604 that chloromethyl vinyl benzene can be prepared via a two step liquid phase reaction whereby isopropyl toluene is chlorinated via ultraviolent light and the subsequently distilled chloromethyl chloroisopropyl benzene is dehydrohalogenated with heat to give chloromethylisopropenylbenzene.
None of the above patents disclose a continuous high temperature vapor phase process for the preparation of substituted vinylbenzyl chloride from substituted ethyl toluene.
The obvious advantages of this process are: the elimination of multiple steps in the preparation of the desired product, the high percentage of total selectivity to substituted vinylbenzyl chloride and its precursors, the ability to use a substituted ethyltoluene which is a much more stable molecule than a substituted vinyltoluene, the elimination of the need for a dehydrogenation step to produce the substituted vinyltoluene needed for the U.S. Pat. No. 2,981,758, the fact that the by-product produced along with the desired substituted vinylbenzyl chloride are all substituted vinylbenzyl chloride precursors and these precursors may be separated and recycled through the reactor to produce additional substituted vinylbenzyl chlorides.